Gravity Falls OneShot – (Pinecest) Who Knows What Might Happen?
by spywi
Summary: Tumblr Prompt: I dunno if this one is a little too weird or not, but I wish you could write a fic where both Dipper and Mabel are at a party and are both pretending to be drunk to try and sleep with their twin. When they wake up the next morning they both feel super guilty and confess tell the other and are incredibly confused
_Gravity Falls [OneShot] – (Pinecest) Who Knows What Might Happen?_

* * *

 _ **Tumblr Prompt**_ _: I dunno if this one is a little too weird or not, but I wish you could write a fic where both Dipper and Mabel are at a party and are both pretending to be drunk to try and sleep with their twin. When they wake up the next morning they both feel super guilty and confess tell the other and are incredibly confused._

[Author's Notes]: I'm going to assume college-age twins for this one. Also, assuming that each twin has a crush on the other, but neither knows the other has a crush on them too. _ **Sorry this took so long! As a thank you for the wait, I made this twice as long as I originally intended it to be.**_ Enjoy!

* * *

"Why exactly are you dragging me to a college party, Mabel?" Dipper asked, tugging at his bangs. He had hoped to wear his old pine tree hat to the party, but Mabel was against it for once, stating that he would stick out like a sore thumb. It was probably just an excuse for her to fix his hair, as she had spent a good twenty minutes trying to get his hair to look somewhat presentable.

"Because you seriously need to unwind, bro," Mabel said, adjusting the hem of her blouse. "You've been stressing over midterms, projects, assignments, meetings, et cetera, et cetera. I'm telling you, we hit the dance floor, we eat some snacks, we avoid the pools of vomit in the hallway, it'll be a nice change of scenery from your normal boring old room."

"Very nice imagery you've planted in my mind, sis. Now I'm even less thrilled to be going."

"C'mon, pleeeease? Do it for me, unwind a little, have some fun?"

"Mabel, you don't even party that often, and we drink even less than that. What makes you think that I'll have fun tonight? Loud party music just reminds me of zombies or those paper clones that I had once made a long time ago."

"Hey, #3 and #4 are doing pretty well back in the ol' Gravity Falls Mansion with McGuckett. Thanks to them being copies of you and your nerdy self, they're pretty much geniuses now," Mabel said. The two of them could just make out their destination up ahead. Dipper pulled the truck over to the side and parked behind a yellow sports car.

"That's ' _genii',_ not 'geniuses,' you know," he said, shutting off the engine.

"Whatever. Leave the math talk at the door and let's get our par-tay on!"

"It's not math talk, it's- _argh!_ " he said grumpily, as Mabel had gotten out of the car and closed the door on him mid-sentence. He grumbled to himself as he unbuckled his seatbelt and followed his sister to the party house.

Mabel was immediately swarmed by a group of her friends and was whisked into the party, with one of the girls pressing a red cup into her hand. Dipper was left to awkwardly stand alone in the hallway, where the music wasn't as loud. He recognized a few of the faces as they passed him by, but the majority of the party-goers were strangers to him.

Dipper leaned back, feeling the music reverberate throughout the wall. He didn't feel comfortable being in situations like this. A while ago, Mabel told him that he had this completely expressionless face whenever he was around new people, so he forced himself to smile. Feeling his cheeks start to hurt, he gave up on smiling.

"Geez, Mabel. Why do you have to be so popular?" he said to no one in particular. Mabel was always the one that everyone was naturally drawn to. Maybe it was the fact that she never stopped smiling, maybe it was her outgoing personality or her bizarre sense of fashion, but Mabel was usually the one that made friends easily. Dipper could never quite emulate his sister's positive personality. The combination of increasingly difficult college exams and annoying group projects only worsened Dipper's outlook on life, and this reflected itself in his general attitude and his facial expressions. His sister once told him in secret that her friend Janine once thought that he was cute, but quickly got over him when she realized that he never really smiled whenever she saw him. That wasn't exactly his fault, as Dipper really only smiled whenever he was alone with Mabel.

In fact, it was only when they were alone together that their real emotions emerged. Sometimes, one of the twins would break down from all the stresses of college, and the other would have to hold them and comfort them until the tears ceased. Mabel, who was struggling more than Dipper in her classes, would be more likely to burst into tears. Dipper would lean against the wall, allowing Mabel to lean against him and cry silently. He'd stroke her shoulder or her hair, whispering words of comfort until she calmed down. Every day for Dipper became a struggle, hoping that it was a good day and that he wouldn't have to see her cry. While it felt nice to successfully comfort her in her moments of negativity and sadness, there would be times where Mabel just couldn't be cheered up at the moment, and Dipper would endlessly worry about her, wondering why he felt so helpless and unable to do anything for her.

Eventually, his protective nature over his sister started growing into something . . . even more. He would call and text her constantly just to make conversation, and more than once he found himself daydreaming about her. As the weeks went on, he would lay awake at night, thinking about Mabel and about how he could cheer her up, and then his thoughts would shift to imagining what it would be like if Mabel would hold his hand, would hug him even longer than they normally did, would. . . kiss him? He'd mentally punch himself for thinking anything remotely close to that, but it would be too late: he'd end up thinking about it over and over until the thought is ingrained in his mindset. Dipper would often watch her go about her daily routine, watching her smile and laugh at his cheesy jokes, and wonder what would have happened if Mabel wasn't his sister. She was already his best friend, but if they weren't siblings then maybe . . .

* * *

"Dude!" came a voice from down the hall, interrupting his thoughts. Not used to being addressed so loudly, Dipper jumped and looked wildly around for the source. A stocky dude wearing a tank top approached him, holding two red plastic cups.

"I believe you are, as the ladies call it, _Dipper Pines_? And by ladies, I mean your sister, 'cuz you look freakin' exactly like her, minus your weird little beard thing you got goin' on there," said the stranger, pointing at Dipper's chin. Dipper scratched the back of his head nervously, suddenly very conscious of the bristles on his face. The guy continued,

"I'm jus' messing with ya. Name's Connor, and this is my place," he said, holding out one of the cups. Dipper accepted it but didn't take a sip.

"Nice place," Dipper said, trying to speak over the music. A new song had started playing, one that was even louder than the last one.

"Ah, thanks, um, Dip? Can I call you Dip? Or do you wanna tell me what your real name is?"

"Just Dipper's fine."

"Sure. Anyways, yeah, thanks. It's my last year here, so I'm makin' the most out of my last few months of college. What about yourself?"

"Second-year."

"Ah, to be young again. It's whatevs though, I'm over it. Just gonna go make sure no one's puking in the bedrooms, in case one of the ladies decides to get freaky," said Connor, winking at Dipper. He sauntered off towards the bedrooms, leaving Dipper alone and clutching a red cup full of alcohol. He peered at the dark liquid within. Was that tequila? Or . . . vodka? Dipper wasn't too well-versed in the different kinds of alcohol, but he was pretty sure that the drink wasn't supposed to be a light pink color.

Dipper headed towards the kitchen, where a group of guys were attempting to play beer pong off the kitchen counter. He ducked around the table and ended up in a side room where he found Mabel, along with a few of her friends. Several empty shot glasses sat in front of his red-faced sister. Mabel was giggling and fidgeting a lot in her seat – something that she'd do a lot when she was drunk – and then she attempted to stand up, only to fall back onto the couch in a fit of laughter. Dipper smiled. At least his sister was a happy drunk, as it made her much more entertaining to talk to.

"You doing okay, sis?"

"Are you KIDDING me?" she said, practically shouting the word at him. "I'm feelin' _fantastic!_ "

She started switching between her normal accent and a foreign accent that he couldn't quite place. It sounded like a combination of French and Spanish with a bit of a German accent for good measure. Mabel pushed a red cup across the table in his direction, which he politely refused, holding up the one that Connor had given him.

"Dip! C'mon! Drink up, broseph, _unwind_ with me and my *hic* friends!" she said.

"Already happenin', Sis," he said, pretending to take a sip. He was definitely not going to be the one that gets pulled over for driving drunk tonight.

One of her friends leaned in close to Dipper, smiling. Dipper did everything in his power to not stare at the girl's chest, as she was wearing a top that had a _very_ low-cut neckline. Instead, he opted to stare at Mabel. His sister was happily chatting away with her friends, having apparently forgotten that Dipper had been talking to her. Her friend with the revealing top started asking him questions.

"You guys are supposed to be twins, so why don't you look like Mabel?" said the friend, squinting at him. She was slurring her words and didn't seem to be seeing straight. Clearly this girl has taken more than a few shots of tequila.

"Um, I don't know. Genetics?" he said hesitantly, refusing the red cup that Mabel kept trying to press into his hands. The other girl started laughing a lot harder than was necessary. Somehow Dipper had ended up on the couch between Mabel and this girl on the couch. He was still pretending to take sips from his own cup, which thankfully was only half full, allowing him to fool those around him into thinking he was buzzed.

" _Mary_! Stop trying to hit on my brother! He's mine!" Mabel said, grabbing Dipper's arm and pulling, almost dragging him off the couch.

"Mae, c'mon, let me have him for tonight," said Mary, pulling on his other hand. Dipper wasn't an expert, but even he could tell that this girl was at least twice as drunk as Mabel was, and seemed even closer to passing out.

"Nu-uh! No one can have my brother except me! C'mon, Sir Dippington! The dance floor awaits!" Mabel said proudly, dragging him to where the music was loudest. Dipper looked behind them. All of Mabel's friends immediately huddled together, whispering excitedly. Great, just what he needed: rumors being spread about him and his sister.

* * *

Mabel danced beautifully for someone with a lot of alcohol in her system. She moved with the grace and beauty of a professional, causing a lot of guys to look her way. Had Dipper been paying attention to those around him, he would have felt extremely jealous and protective. In this moment however, Mabel's movements have completely hypnotized him. The music eventually shifted to a much slower song, and Mabel pulled him aside so that they could get some air. While Mabel started browsing the snack table, Dipper strode over to the drinks counter and found a water bottle. Emptying it into a new red cup, he took a grateful swig of water. He hadn't had anything to drink all night, so his face was getting as red as Mabel's was.

"Hey, Dip," Mabel said, coming over to him. She put her arms around his own. As soon as she touched his arm, a mini electric surge went through his entire body.

"Y-Yeah?" he said, looking at her. She was staring so intensely at him that he felt like his face was going to burst into flames. Try as he might, he couldn't think of another word to describe his sister other than _beautiful._

Mabel didn't answer him, instead taking him by the hand and leading him into an open door. Mabel locked the door, pulling him over to the bed. Dipper's head was spinning. He never expected any of this to be happening so quickly. Sure, he's had somewhat of a crush on his sister, but going straight from a crush to _this_ is a bit sudden. His brain went into overdrive, thinking about every possible outcome that could come from this situation, and then his mind immediately shut down as Mabel started pressing her lips against his.

 _Whoa whoa WHOA!_ he thought frantically. _What's happening? Why's this happening? I CAN'T believe this is happening! This is . . ._

Mabel moaned into his mouth, stopping Dipper from forming a coherent sentence in his head. She pulled at his collar, kissing him as if her life depended on it.

"Mabe-" Dipper would mumble when he had managed to break away, but Mabel would cut him off with another kiss. Finally, Mabel released his shirt and pushed him down onto the bed.

"I've wanted this for so long," Mabel breathed into his ear. Dipper, still catching his breath, couldn't respond. She kissed his lips once more, and then left a line of kisses along the side of his face to his ear. She gave his earlobe a small lick, and then started suckling his ear, sending a wave of shivers down Dipper's spine. He never knew he was sensitive there until this very moment.

Mabel worked her way down Dipper's neck, hitting all his sensitive spots and causing him to squirm and moan into her shoulder. She seemed to know exactly where he was ticklish, and then giggling as his body twitched when she hit a sweet spot.

"Mabes, I- _ah!_ This isn't a good idea for us to-" he started, but he was shushed by Mabel placing a finger on his mouth.

" _What_? 'Cuz you're my brother? 'Cuz we're in some random bed in a random house in the middle of a party with people just outside? 'Cuz it's _wrong_?" she said, pulling down the neck of his shirt to suck at his pulse point. "Well guess what, Dip? Right now, I don't care. I've wanted this for so long that I'm going crazy. I want this and I want everything and I want _you!_ "

She suddenly sat up and looked into his eyes. Dipper looked at her flushed face and her almost frantic expression and saw a fire in it that he had never seen before. She was serious. Dead serious.

"Dipper," Mabel said. "I love you. And I've been around you long enough that I can tell that you love me too. So please, let me have this, because I'm 100% sure that you want this too."

Dipper nodded slowly, and then sat up, facing her. He placed a gentle hand on her face, and she leaned into his palm. She kissed his rough skin, snuggling her face into his open hand, smiling as he started brushing her cheek with a thumb.

"Mabel, are you sure you want me? We're gonna have a hell of a lot of problems if this ever gets out. I don't want to end up hurting you."

"Dip, it's always been you and me, through thick and thin. Whatever happens, we go through it together. Like always. I just need you to-"

She stopped talking, as Dipper kissed her back properly for the first time. She mimicked his hand, placing hers on his cheek. Dipper poured out all his pent up emotions into the kiss, hoping that he would be able to convey to her everything he had been feeling about her. Every moment that he had imagined her lips on his, every night that he lay awake thinking about her, every second that he spent worrying about her, he put as much passion as he could into this connection with his sister.

"I love you," Dipper breathed, gently placing his forehead against hers. She smiled, and then sat up straight and began to pull up her blouse. Dipper couldn't help but stare at in the direction of her bra, which, of course, had an insane amount of sequins sewn into it. Mabel giggled some more.

"What? The sparkles hypnotizing you?" she said, giving her upper body an experimental shake. The sequins caught the light of the bedside lamp, glittering in his face. Mabel took his hand and placed it underneath the fabric. She gasped as his fingers brushed against an erect nipple.

"Geez, Dipstick, why's your hand gotta be so cold? Nerves?"

"Don't blame me, I don't know," he replied, giving her breast an experimental squeeze. Mabel let out a louder moan than she expected. Using his other hand, Dipper lifted up her bra completely, exposing everything.

"Whoa," Dipper said, taking a breast in each hand and massaging gently. The coldness of his hands only made Mabel more sensitive, causing her to squirm and moan even more than how Dipper had just earlier.

"Dipper," Mabel said quietly, stars in her eyes. She kissed him fiercely, and then grabbed one of his hands and slowly started dragging it lower and lower on her body until . . .

 _ **SLAM**_

There was suddenly a loud knock on the door. The twins jumped, almost falling off the side of the bed. Another loud knock, and then then knob started jiggling. Mabel grabbed the sheets and pulled it over themselves, both of them quickly laying down underneath the blanket. The door flew open and crashed into the wall beside it.

"Aw, man, the room's occupied. Bummer," said a voice that Dipper recognized as Connor's.

"Don't worry about it, baby, we can always try somewhere else," said another familiar and very drunk-sounding voice. In the light filtering through the blanket, Mabel mouthed out the name _Mary_. Dipper nodded, and then kissed her quickly to ensure she stayed quiet. Connor and Mary shut the door behind them, and the Pines twins could hear the two of them stumbling down the hallway. Mabel sighed, and then fixed her bra and top and hugged Dipper. He hugged her back, and the two of them, surprisingly tired out from the night's adventures, fell asleep in each other's arms. Dipper drifted off, the last thought on his mind being: _Is it me, or does Mabel's breath suddenly not smell like alcohol?_

* * *

Dawn broke, and the light spilled through the open window onto the twins. Mabel had shifted in her sleep, and one leg as well as her arms were now draped around her brother. She was the first to wake, sitting up and looking around their surroundings. She poked Dipper's cheek, and he woke up immediately. They looked at each other, and as the memories of last night caught up with them, they both began speaking loudly

"Mabel, I-ah, um, we, um . . ."

"We kissed last night. We made it to second base. We almost . . . did . . . it, Dip I'm so sorry . . ."

"We shouldn't have let it get that far, Mabes, I shouldn't have tried anything, we. . ."

"I shouldn't have tried to take advantage of you, Dipper, you were drunk, and I just thought that we could . . ."

"Wait, say that again?" Dipper said, confused.

"You were drunk, and I just thought that since you tend to not remember things when you're drunk . . ."

"Mabel, I wasn't drunk. I thought you were drunk."

" _Wha?!_ But whenever you get drunk, you get all moody and red-faced, and you start being even more anti-social and awkward than usual."

"And you were all red in the face and giggly. You're the happy drunk here, I couldn't even tell that – ah, geez, that explains why your breath didn't smell like alcohol last night. I wasn't even thinking about that," said Dipper, rubbing his temples.

"So what you're saying is," Mabel said, putting the pieces together. "We both thought the other was drunk, and then we pretended to be drunk ourselves, and then we kissed and almost . . . slept with each other. What exactly did we get ourselves into, Dip?"

"I have no clue. Honestly, I don't know what to do."

"Can . . . can we try it?"

"Try . . . what, exactly?" he asked nervously. Mabel took his hand.

"Dip, will you be my boyfriend? And my brother, but of course you'd be my brother, unless you want to stop being that, in which case you'd just be my boyfriend. Or you can just be my brother and not my boyfriend, I mean, that's up to you-"

Dipper kissed her, stopping her mid-sentence. Mabel kissed back, putting her arms around him and holding him for dear life.

"Wow," Mabel sighed as soon as she got some air. "I take that as a yes?"

"Leave it to Mabel Pines to be the one to ask out the guy."

"Yeah, well, I try," Mabel giggled. "I mean, if I see a cute guy, I kinda start plotting exactly how I want to ask them out. This plan has sort of been in the works in my mind as soon as I got with my friends at the couch."

"Point taken. I just thought you were drunk," said Dipper. Mabel smacked him in the shoulder.

"You dork."

"Right back at ya, sis-friend."

"Hmm, doesn't have quite the same ring as bro-friend. You sure you're not still drunk, Dip?" she teased. He responded by squeezing her left breast, causing her to yelp.

" _Dipper!_ "

"Admit it, you like it," he grinned. Mabel gave a sarcastic laugh, and then reached down and squeezed the apparent bulge that had formed in his jeans. Dipper immediately squirmed, letting out a sharp breath.

"Let's get back to the dorm, so that we can finish what we started last night. Then you'll see exactly how much I like it," Mabel said, giving him a sultry look. Dipper smiled.

"You planning what I think you're planning?" he asked. Mabel shrugged.

"I mean, it's you, me and nobody else for the next few hours in an empty dorm. Who knows what might happen?" she responded. Dipper took her hand, and the two of them headed for the car.


End file.
